Comparative Study On The Bioleaching Of Chalcopyrite By Acidithiobacillus Ferrooxidans And On Its Different Expression Of Gene Afe0022

Acidithiobacillus ferrooxidans, is an important microorganism in bioleaching industry. In bioleaching process, A. ferrooxidans can survive in a higher concentration of heavy metal ion, so the efficiency of heavy metal ion to A. ferrooxidans has been studied wildly. But the underlying genetic mechanism is still largely unknown.In this paper, the tolerance on Cu2+ of the A. ferrooxidans strain DC, DY26 and DY15 was studied, the results showed that the tolerance on Cu2+ is quite different among the strain DC, DY26 and DY15, the tolerance on Cu2+ of the strain DY26 is 5.5 times more than the strain DC while the tolerance on Cu2+ of the strain DY15 is 10 times.In this research, the relationship between the gene Afe0022 (the Locus is AFE₀022) and copper homeostasis was investigated. The cation channel protein gene Afe0022 of strain DC, strain DY26 and strain DY15 were successfully cloned and sequence analysis indicated that there is one amino acid that is R (407) of strain DY26 which is different from the standard strain ATCC23270; though there are 11 bases of strain DY15 which are different from the standard strain ATCC23270, there are no amino acids changes of strain DY15 because of degeneracy, as the same as strain DC. The result of BLAST in the NCBI indicated that protein AFE0022 has the highest homology to voltage-gate potassium channel protein of A. ferrooxidans ATCC53993.Real-time PCR was used to detect the different expression of Afe0022 in different concentration of copper ions among three strains DC, DY26 and DY15. The results showed that Afe0022 was intensively responsive to copper, the expression was enhanced while the Cu2+ concentration increased. Moreover, the expression of Afe002'2 increase up to 47.18 times in strain DC and 75.53 times in strain DY26 and 112.02 times in strain DY15 at the highest concentration the bacteria could tolerate.The effects of different initial concentrations of copper ion to chalcopyrite concentrate bioleaching were investigated with Acidithiobacillus ferrooxidans DY15, DY26 and DC. In the leaching experiment, strain DY15 had the highest bioleaching efficiency on chalcopyrite concentrate while strain DC had the least bioleaching efficiency,but the mixed cultures containing 3 strains exhibited the highest efficiency than the pure cultures alone.All of these results confirmed that Afe0022 plays important role in copper homeostasis. The results lead us to a further step for understanding the copper homeostasis mechanism in this extremophilic microorganism, and provide a theoretical foundation for us to upgrade the bioleaching technique through improving copper resistance of A. ferrooxidans, and it has certain practical significance for bioleaching.